diff --git a/4chan-X.user.js b/4chan-X.user.js
index be5d93ffa..faac376ed 100644
--- a/4chan-X.user.js
+++ b/4chan-X.user.js
@@ -1112,11 +1112,7 @@
       if ('visibilityState' in document) {
         return;
       }
-      if ('webkitVisibilityState' in document) {
-        prefix = 'webkit';
-      } else if ('mozVisibilityState' in document) {
-        prefix = 'moz';
-      } else {
+      if (!(prefix = ('webkitVisibilityState' in document ? 'webkit' : 'mozVisibilityState' in document ? 'moz' : void 0))) {
         return;
       }
       property = prefix + 'VisibilityState';
diff --git a/lib/polyfill.coffee b/lib/polyfill.coffee
index 0c098b212..5a5b48e10 100644
--- a/lib/polyfill.coffee
+++ b/lib/polyfill.coffee
@@ -4,12 +4,12 @@ Polyfill =
   visibility: ->
     # page visibility API
     return if 'visibilityState' of document
-    if 'webkitVisibilityState' of document
-      prefix = 'webkit'
-    else if 'mozVisibilityState' of document
-      prefix = 'moz'
-    else
-      return
+    return unless prefix = (
+      if 'webkitVisibilityState' of document
+        'webkit'
+      else if 'mozVisibilityState' of document
+        'moz'
+    )
 
     property = prefix + 'VisibilityState'
     event    = prefix + 'visibilitychange'